This invention relates to a regulator for water base paint which is used in a painting line of automobiles or the like.
In a conventional painting line of automobiles or the like, paint is constantly kept circulating in order to prevent the pigment and metallic particles in the paint from settling. A branch is made at a required position and the pressure of the paint is regulated by a regulator to a constant pressure before the paint is supplied to a painting head.
The construction of the regulator is as follows. Inside a casing having an inlet port and an outlet port, a paint chamber is provided in fluid communication with the outlet port. Between the paint chamber and the inlet port, there are provided a valve seat and a valve which is movable to be pressed against the valve seat or away therefrom. The valve is moved to be pressed against the valve seat or away therefrom in interlocking with a diaphragm or the like which is subjected to an internal pressure of the paint chamber, whereby the delivery or outlet pressure of the paint from the outlet port is kept constant.
It has become recent practice to use water base paint in order to prevent the environmental pollution. In such a case, the regulator is required to have corrosion resistance. Therefore, a regulator for water base paint has been developed in which the casing, the valve seat and the valve are made of stainless steel such as SUS304 or the like. In this kind of regulator, the corrosion resistivity may be satisfied. However, since the valve seat and the valve are made of the same material having the same hardness, fragile portions, if any, in the texture of the valve seat or the valve may lead to the following problems. Namely, by repeated striking of the valve against the valve seat, wear progresses in a concentrated manner at the fragile portions. This partial or uneven wear deteriorates the sealing characteristics or fluid tightness between the valve seat and the valve in a short time. This results in a shortened cycle of replacing the valve seat and the valve. It also happens that residual matters of the water base paint are likely to be adhered to these members, thereby resulting in a shortened cycle of performing maintenance.